Table 1: Comparison of analytical approximations with the exact one for buckling loads.

(a)

(b)

(c)

(d)

20°

1.0154

1.0152 (0.0197)

1.0155 (0.0098)

1.0155 (0.0098)

40°

1.0637

1.0609 (0.2632)

1.0648 (0.1034)

1.0647 (0.0940)

60°

1.1517

1.1371 (1.2677)

1.1567 (0.4341)

1.1576 (0.5123)

80°

1.2939

1.2437 (3.8797)

1.3056 (0.9042)

1.3164 (1.7389)

100°

1.5184

1.3808 (9.0622)

1.5318 (0.8825)

1.5890 (4.6496)

120°

1.8848

1.5483 (17.8534)

1.8615 (1.2362)

2.0821 (10.4680)

Number inside the bracket ( ) is the % relative error computed.
(a)Results by the exact theory [12].
(b)Results by the HPM truncated to the first order.
(c)Results by the HPM truncated to the second order.
(d)Results by the SAA.